package org.wangzs.blog.common;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.wangzs.blog.util.Const;

public class CaptchaServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;

	// 图片宽度
	private static final int WIDTH = 60;
	// 图片高度
	private static final int HEIGHT = 32;
	// 字符距上边框的距离
	private static final int PADDINGTOP = 20;
	// 字符距左边框的距离
	private static final int PADDINGLEFT = 6;
	// 字符间距
	private static final int SPACING = 10;

	private static char[] captchars = new char[] { 'a', 'b', 'c', 'd', 'e',
			'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
			's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '1', '2', '3', '4', '5',
			'6', '7', '8', '9', '0', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
			'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U',
			'V', 'W', 'X', 'Y', 'Z' };

	Color getRandColor(int fc, int bc) {// 给定范围获得随机颜色
		Random random = new Random();
		if (fc > 255)
			fc = 255;
		if (bc > 255)
			bc = 255;
		int r = fc + random.nextInt(bc - fc);
		int g = fc + random.nextInt(bc - fc);
		int b = fc + random.nextInt(bc - fc);
		return new Color(r, g, b);
	}

	public void doGet(HttpServletRequest request, HttpServletResponse response) {
		// 设置页面不缓存
		response.setHeader("Pragma", "No-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);
		response.setContentType("image/JPEG");

		// 在内存中创建图象
		BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
				BufferedImage.TYPE_INT_RGB);

		// 获取图形上下文
		Graphics g = image.getGraphics();

		// 生成随机类
		Random random = new Random();

		// 设定背景色
		g.setColor(getRandColor(200, 250));
		g.fillRect(0, 0, WIDTH, HEIGHT);

		// 设定字体
		g.setFont(new Font("Times New Roman", Font.PLAIN, 22));

		// 画边框
		// g.setColor(new Color());
		// g.drawRect(0,0,width-1,height-1);

		// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
		g.setColor(getRandColor(160, 200));
		for (int i = 0; i < 50; i++) {
			int x = random.nextInt(WIDTH);
			int y = random.nextInt(HEIGHT);
			int xl = random.nextInt(12);
			int yl = random.nextInt(12);
			g.drawLine(x, y, x + xl, y + yl);
		}

		// 取随机产生的认证码(4位数字)
		String sRand = "";
		for (int i = 0; i < 4; i++) {
			int car = captchars.length - 1;
			String rand = String.valueOf(captchars[random.nextInt(car) + 1]);
			sRand += rand;
			// 将认证码显示到图象中
			g.setColor(new Color(20 + random.nextInt(110), 20 + random
					.nextInt(110), 20 + random.nextInt(110)));
			g.drawString(rand, SPACING * i + PADDINGLEFT, PADDINGTOP);
		}

		// 将认证码存入SESSION
		request.getSession().setAttribute(Const.SESSION_CAPTCHA, sRand);

		// 图象生效
		g.dispose();
		// 输出图象到页面
		try {
			ImageIO.write(image, "JPEG", response.getOutputStream());
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}
